Method of making a nanostructure and nanostructured articles

ABSTRACT

A method of making a nanostructure and nanostructured articles by depositing a layer to a major surface of a substrate by plasma chemical vapor deposition from a gaseous mixture while substantially simultaneously etching the surface with a reactive species. The method includes providing a substrate; mixing a first gaseous species capable of depositing a layer onto the substrate when formed into a plasma, with a second gaseous species capable of etching the substrate when formed into a plasma, thereby forming a gaseous mixture; forming the gaseous mixture into a plasma; and exposing a surface of the substrate to the plasma, wherein the surface is etched and a layer is deposited on at least a portion of the etched surface substantially simultaneously, thereby forming the nanostructure. The substrate can be a (co)polymeric material, an inorganic material, an alloy, a solid solution, or a combination thereof. The deposited layer can include the reaction product of plasma chemical vapor deposition using a reactant gas comprising a compound selected from the group consisting of organosilicon compounds, metal alkyl compounds, meal isopropoxide compounds, metal acetylacetonate compounds, metal halide compounds, and combinations thereof. Nanostructures of high aspect ratio and optionally with random dimensions in at least one dimension and preferably in three orthogonal dimensions can be prepared.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2014/047782, filed Jul. 23, 2014, which claims priority to U.S.Application No. 61/858,670, filed Jul. 26, 2013; US Application No.61/867,733, filed Aug. 20, 2013; and U.S. Application No. 62/018,761,filed Jun. 30, 2014, the disclosures of which are incorporated byreference in their entirety herein.

FIELD

Methods are disclosed for producing nanostructures on surfaces ofarticles, more particularly, methods for producing nanostructures onsurfaces of (co)polymeric substrates.

BACKGROUND

Nanostructures have been found to impart useful properties on surfacesof articles. These useful properties include useful optical properties;such as, for example, reflection reduction of plastic substrates; usefulphysical properties, such as, for example, surface modification forimproved adhesion; and useful structural properties for creatingfeatures on surfaces that can be useful in, for example, drug delivery.

A number of methods have been used to produce nanostructures on surfacesof non-(co)polymeric substrates. For example, plasma etching is a usefulmethod that has been used to generate nanostructures. A particular typeof plasma etching, reactive ion etching (RIE) has been widely employedin the semiconductor industry to produce submicron features on siliconsubstrates useful in electronics. Recently, high density plasmaprocesses have been developed that can produce nanostructures on siliconin the sub-100 micrometer range. The semiconductor industry is currentlyworking on the fabrication of nanoscale features on silicon wafers witharound 40 nm resolution, using patterning and pattern transfer based onadvanced plasma processing tools.

Plasma treatment has also been used to produce antireflective surfaceson (co)polymeric substrates, including transparent (co)polymericsubstrates. Many of these treatments are batch processes and can produceonly limited antireflective regions on the substrates. Co-pending andcommonly assigned PCT Pat. Pub. WO 2011/139593 describes methods toproduce nanostructures on surfaces in a substantially continuous manner.

SUMMARY

Although plasma processes have been used to produce nanostructures onsurfaces of non-conductive substrates such as (co)polymeric films, whenany of the individual dimensions of the nanostructures reach a scalebelow about 200 micrometers, charging effects of the surface features bythe plasma generally prevent pattern transfer of features having highaspect ratios.

Furthermore, known methods for creating sub-wavelength (e.g. nanoscale)surface structure tend to be complicated and expensive batch processes.For example, the method disclosed in U.S. Pat. Publ. No. 2005/0233083(Schultz et al.) involves bombarding a (co)polymeric surface with anAr/O₂ plasma under vacuum conditions of less than 0.5 mTorr (0.067N/m²). This requirement of extreme vacuum conditions severely limits thecommercial viability of this method, particularly for continuous,roll-to-roll production of nanostructured (co)polymeric substrates. Inaddition, U.S. Pat. No. 4,374,158 (Taniguchi et al.) describes a gasactivation method for creating sub-wavelength surface structures. Thisbatch process employs a plasma etcher to isotropically etch samples inan oxygen-containing gas. The resulting isotropically etched surfacesrequire an additional coating to provide sufficient durability forpractical applications. Thus, there is a heretofore unmet need toprovide methods for producing nanostructured surfaces on non-conductivesubstrates, more particularly durable, high aspect ratio nanostructuredfeatures on (co)polymeric substrates, in a single stage, continuousoperation.

In various exemplary embodiments described herein, the disclosed methodsmay be used for creating nanostructures on substrates, includingnon-conductive (co)polymeric substrates, and nanostructured articles, ina continuous, roll-to-roll process. The disclosed methods may be appliedto large areas of substrates such as, for example, rolls of plasticsubstrates. Films and surfaces produced by the disclosed methods may beuseful, for example, in liquid crystal (LCD) or light-emitting-diode(LED) displays, for light extraction, for solar applications, forsurface adhesion modification, and for chemical catalysis. The disclosedmethods may also produce surfaces that can be hydrophilic, hydrophobic,antistatic, conductive, antifogging, or even antimicrobial.

Thus, in one aspect, the disclosure provides a method of making ananostructure that includes providing a substrate, mixing a firstgaseous species capable of depositing a layer onto the substrate whenformed into a plasma with a second gaseous species capable of etchingthe substrate when formed into a plasma, thereby forming a gaseousmixture, forming the gaseous mixture into a plasma, and exposing asurface of the substrate to the plasma, wherein the surface is etchedand a layer is deposited on at least a portion of the etched surfacesubstantially simultaneously, thereby forming a nanostructure.

Further, when the substrate is a fluoropolymer, the above techniquesprovide exceptional adhesion to adjacent layers that may be applied bycoating, laminating, or compression onto the nanostructure. Thus, inanother aspect, the disclosure provides that where the substrate is afluoropolymer, the method may further comprise contacting thenanostructure with a film or a film-forming material so as to form amulti-layered laminate. Fluoropolymers are notoriously difficult to makeadhesion to, and with the techniques of this disclosure, it is possibleto form a multilayered laminate where the adhesive strength between thefilm and the nanostructure is greater than the cohesive strength of thefilm.

In some exemplary embodiments of the foregoing, the substrate can be anon-conductive substrate, for example a substrate including a(co)polymer (e.g. a (co)polymeric film), a fiber, a glass, a composite,a microporous membrane and combinations thereof. In certain suchexemplary embodiments, the substrate can be transparent to visible lightand can include (co)polymers such as poly(methyl methacrylate),poly(ethylene terephthalate), polycarbonate, cellulose, triacetate,polyamide, polyimide, a fluoropolymer, a polyolefin, a siloxane(co)polymer, a cyclic olefin (co)polymer, a polyurethane andcombinations thereof.

In certain such exemplary embodiments, the first gaseous speciesincludes a compound selected from the group consisting of organosiliconcompounds, metal alkyl compounds, metal isopropoxide compounds, metaloxide compounds, metal acetylacetonate compounds, metal halidecompounds, and combinations thereof. The second gaseous species can be,in some such exemplary embodiments, oxygen, a fluorocarbon, nitrogentrifluoride, sulfur hexafluoride, chlorine, hydrochloric acid, methane,and combinations thereof. In some exemplary embodiments, an inertcarrier gas, such as argon, can typically be mixed in with the secondgaseous species.

In some particular exemplary embodiments of any of the foregoing, thenanostructure can have a dimension of less than about 400 nanometers(nm). In certain such exemplary embodiments, the nanostructure can havea dimension of less than about 40 nm. Articles that have at least onenanostructured surface can also be made by the disclosed methods.

In some exemplary embodiments of any of the foregoing, thenanostructured surfaces prepared by the provided method can exhibit asignificant reduction in reflectance compared to an unstructured surfacecomprising the same materials. In additional exemplary embodiments ofany of the foregoing, the nanostructured articles can be durable andpossess scratch resistance.

In certain exemplary embodiments of any of the foregoing, the disclosedmethods can be carried out at moderate vacuum conditions (for example,between about 5 mTorr (0.67 N/m²) and about 10 mTorr (1.33 N/m²)). Insome such embodiments, the disclosed methods can be carried out in acontinuous process. In some particular embodiments, the disclosedmethods can also be carried out as a roll-to-roll process, at a singlestation positioned in a continuous web transport line. In such exemplaryembodiments, the disclosed methods satisfy a heretofore unmet need inthe art for a method of making durable, high aspect ratio nanostructuredfeatures on non-conductive substrates, for example (co)polymeric films,that is continuous and comparatively inexpensive.

Various exemplary embodiments of the present disclosure are furtherillustrated by the following listing of embodiments, which should not beconstrued to unduly limit the present disclosure:

LISTING OF EXEMPLARY EMBODIMENTS

A. A method of making a nanostructure, comprising:

providing a substrate;

mixing a first gaseous species capable of depositing a layer onto thesubstrate when formed into a plasma, with a second gaseous speciescapable of etching the substrate when formed into a plasma, therebyforming a gaseous mixture;

forming the gaseous mixture into a plasma; and

exposing a surface of the substrate to the plasma, wherein the surfaceis etched and a layer is deposited on at least a portion of the etchedsurface substantially simultaneously, thereby forming a nanostructure.

B. A method of making a nanostructure according to embodiment A, whereinthe substrate comprises a (co)polymeric material, an inorganic material,an alloy, a solid solution, and combinations thereof.

C. A method of making a nanostructure according to embodiment B, whereinthe (co)polymeric material comprises a (co)polymer selected frompoly(methyl methacrylate), poly(ethylene terephthalate), polycarbonate,cellulose, triacetate, polyamide, polyimide, a fluoropolymer, apolyolefin, a siloxane (co)polymer, a cyclic olefin (co)polymer, or apolyurethane, and combinations thereof.D. A method making a nanostructure according to embodiment C, whereinthe (co)polymer is a polytetrafluoroethylene fluoropolymer and thesurface of the substrate is substantially colorless after exposure tothe plasma.E. A method of making a nanostructure according to embodiment C, whereinthe substrate comprises a transparent (co)polymer.F. A method of making a nanostructure according to any precedingembodiment, wherein the first gaseous species comprises a compoundselected from the group consisting of organosilicon compounds, metalalkyl compounds, metal isopropoxide compounds, metal oxide compounds,metal acetylacetonate compounds, and metal halide compounds, andcombinations thereof.G. A method of making a nanostructure according to embodiment F, whereinthe organosilicon compounds comprise tetramethylsilane, trimethylsilane,hexamethyldisiloxane, tetraethylorthosilicate, or a polyhedraloligomeric silsesquioxane, and combinations thereof.H. A method of making a nanostructure according to any precedingembodiment, wherein the second gaseous species comprises oxygen, afluorocarbon, nitrogen trifluoride, sulfur hexafluoride, chlorine,hydrochloric acid, methane, and combinations thereof.I. A method of making a nanostructure according to embodiment H, whereinthe fluorocarbon is selected from tetrafluoromethane, perfluoropropane,and combinations thereof.J. A method of making a nanostructure according to any precedingembodiment, wherein the gaseous mixture further comprises argon.K. A method of making a nanostructure according to any precedingembodiment, wherein the nanostructure has a dimension of less than about400 nanometers.L. A method of making a nanostructure according to embodiment K, whereinthe nanostructure has a dimension of less than about 40 nanometers.M. A method of making a nanostructure according to any precedingembodiment, performed in a substantially continuous manner.N. An article made from the method according to any preceding methodembodiment.O. An article according to embodiment N, having a Reflectance of lessthan 3% and a Haze Delta of less than 0.5%.P. An article according to embodiment O, having a Reflectance of lessthan 2% and a Haze Delta of less than 0.5%.Q. An article according to embodiment P, having a Reflectance of lessthan 1% and a Haze Delta of less than 0.5%.R. An article according to any one of embodiments N, O, P or Q, whereinthe etched surface has at least one nanostructure with an aspect ratiogreater than 2:1.S. An article according to embodiment R, wherein the etched surface hasat least one nanostructure with an aspect ratio greater than 15:1.T. An article according to any one of embodiments N, O, P, Q, R or S,wherein the deposited species is present over substantially the entireetched surface.U. The article according to any one of embodiments N, O, P, Q, R, S, orT, wherein the concentration of the deposited species variescontinuously according to the depth from the exposed surface.V. The article according to any one of embodiments N, O, P, Q, R, S, T,or U, wherein the exposed surface comprises silanol groups.W. The article according to any one of embodiments N, O, P, Q, R, S, T,U, or V, further comprising a layer of pressure sensitive adhesiveadhered to the exposed surface.X. The article according to embodiment W, wherein the pressure sensitiveadhesive and the substrate are UV stable.Y. The article according to any one of embodiments N, O, P, Q, R, S, T,U, V, W or X, wherein the exposed surface has a pattern that is randomin at least one dimension.Z. The article according to embodiment Y, wherein the exposed surfacehas a pattern that is random in three orthogonal dimensions.AA. A method of making a nanostructure according to embodiment A,wherein the substrate is a fluoropolymer, and the method furthercomprises contacting the nanostructure with a film or a film-formingmaterial so as to form a multi-layered laminate.AB. A method of forming a multilayered laminate, comprising:

providing a fluoropolymer film having at least a first surface,

forming a nanostructure on a the first surface, and

contacting the nanostructure with a film or a film-forming material soas to form a multi-layered laminate.

AC. A method of forming a multilayered laminate according to embodimentAB, wherein the adhesive strength between the film and the nanostructureis greater than the cohesive strength of the film.

AD. An article made from the method according to any one of embodimentsAB and AC.

Various aspects and advantages of exemplary embodiments of thedisclosure have been summarized. The above Summary is not intended todescribe each illustrated embodiment or every implementation of thepresent certain exemplary embodiments of the present disclosure. TheDrawings and the Detailed Description that follow more particularlyexemplify certain preferred embodiments using the principles disclosedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which it is to beunderstood by one of ordinary skill in the art that the drawingsillustrate certain exemplary embodiments only, and are not intended aslimiting the broader aspects of the present disclosure.

FIGS. 1a-1b are sequential schematic views of an embodiment of anarticle made by the provided method.

FIG. 2 is a first fragmentary perspective view of a coating apparatususeful in the present invention.

FIG. 3 is a second fragmentary perspective view of the apparatus of FIG.1 taken from a different vantage point.

FIG. 4a is a fragmentary perspective view of another embodiment of thecoating apparatus removed from its gas containing chamber.

FIG. 4b is a second perspective view of the apparatus of FIG. 4a takenfrom a different vantage point.

FIG. 5 is a micrograph of the surface of a film etched according toExample 1 below.

FIG. 6 is a micrograph of the surface of a film etched according toExample 4 below.

FIG. 7 is a micrograph of the surface of a film etched generallyaccording to the disclosure of WO2011/139593 in Comparative Example 4Cbelow so as to contrast the surface morphology depicted in FIG. 6.

FIGS. 8a and 8b are graphs of atomic concentration vs sputter time forembodiments of articles made according to Example 4 and ComparativeExample 4C below respectively.

FIG. 9 is a cross section view of a multilayered laminate including afluoropolymer substrate provided with a nanostructure, joined withanother film.

FIG. 10 is a cross section view of a multilayered laminate including afluoropolymer substrate provided with a nanostructure, joined with anadhesive layer, the adhesive layer in turn adhered to a surface to beprotected.

FIG. 11 is a cross section view of a multilayered laminate including afluoropolymer substrate provided with a nanostructure on each of twomajor surfaces, each of the nanostructures joined with an adhesivelayer, each adhesive layer in turn adhered to a surface to form anarticle.

Repeated use of reference characters in the specification and drawingsis intended to represent the same or analogous features or elements ofthe disclosure. While the above-identified drawings, which may not bedrawn to scale, set forth various embodiments of the present disclosure,other embodiments are also contemplated, as noted in the DetailedDescription.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying setof drawings that form a part of the description hereof and in which areshown by way of illustration several specific embodiments. It is to beunderstood that other embodiments are contemplated and may be madewithout departing from the scope or spirit of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein. At the very least, and not as an attempt tolimit the application of the doctrine of equivalents to the scope of theclaimed embodiments, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques. In addition, the use of numericalranges with endpoints includes all numbers within that range (e.g. 1 to5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any narrower range orsingle value within that range.

Glossary

Certain terms are used throughout the description and the claims that,while for the most part are well known, may require some explanation. Itshould be understood that, as used herein:

The terms “about” or “approximately” with reference to a numerical valueor a shape means +/−five percent of the numerical value or property orcharacteristic, but also expressly includes any narrow range within the+/−five percent of the numerical value or property or characteristic aswell as the exact numerical value. For example, a temperature of “about”100° C. refers to a temperature from 95° C. to 105° C., but alsoexpressly includes any narrower range of temperature or even a singletemperature within that range, including, for example, a temperature ofexactly 100° C.

The term “substantially” with reference to a property or characteristicmeans that the property or characteristic is exhibited to within 98% ofthat property or characteristic, but also expressly includes any narrowrange within the two percent of the property or characteristic, as wellas the exact value of the property or characteristic. For example, asubstrate that is “substantially” transparent refers to a substrate thattransmits 98-100% of incident light.

The terms “a”, “an”, and “the” include plural referents unless thecontent clearly dictates otherwise. Thus, for example, reference to amaterial containing “a compound” includes a mixture of two or morecompounds.

The term “or” is generally employed in its sense including “and/or”unless the content clearly dictates otherwise.

The term “molecular weight” as used throughout this specification meansweight average molecular weight unless expressly noted otherwise.

The term “monomer” means a relatively low molecular weight material(i.e., having a molecular weight less than about 500 g/mole) having oneor more radically polymerizable groups.

The term “oligomer” means a relatively intermediate molecular weightmaterial having a molecular weight in a range from about 500 g/mole toabout 10,000 g/mole.

The term “(co)polymer” means a relatively high molecular weight materialhaving a molecular weight of at least about 10,000 g/mole (in someembodiments, in a range from 10,000 g/mole to 5,000,000 g/mole). Theterms “(co)polymer” or “(co)polymers” includes homopolymers andcopolymers, as well as homopolymers or copolymers that may be formed ina miscible blend, e.g., by co-extrusion or by reaction, including, e.g.,transesterification. The term “(co)polymer” includes random, block andstar (e.g. dendritic) (co)polymers.

The term “(meth)acrylate” with respect to a monomer, oligomer or means avinyl-functional alkyl ester formed as the reaction product of analcohol with an acrylic or a methacrylic acid.

The term “glass transition temperature” or “T_(g)” refers to the glasstransition temperature of a (co)polymer when evaluated in bulk ratherthan in a thin film form. In instances where a (co)polymer can only beexamined in thin film form, the bulk form T_(g) can usually be estimatedwith reasonable accuracy. Bulk form T_(g) values usually are determinedby evaluating the rate of heat flow vs. temperature using differentialscanning calorimetry (DSC) to determine the onset of segmental mobilityfor the (co)polymer and the inflection point (usually a second-ordertransition) at which the (co)polymer can be said to change from a glassyto a rubbery state. Bulk form T_(g) values can also be estimated using adynamic mechanical thermal analysis (DMTA) technique, which measures thechange in the modulus of the (co)polymer as a function of temperatureand frequency of vibration.

The term “anisotropic” refers to a feature or structure having a heightto width (that is, average width) ratio (aspect ratio) of about 1.5:1 orgreater (preferably, 2:1 or greater, more preferably, 5:1 or greater);

The term “nanoscale” refers to features or structures having acharacteristic length, width or height of no more than one micrometer(1,000 nanometers), for example, between about 1 nanometer (nm) andabout 1,000 nm, more preferably between about 1 nm and 500 nm, mostpreferably between about 5 nm and 300 nm);

The term “nanostructure” or “nanostructured” refers to an article havingat least one nanoscale feature or structure, and preferably a pluralityof nanoscale features or structures; and

The term “plasma” refers to a partially ionized gaseous or fluid stateof matter containing electrons, ions, neutral molecules, and freeradicals.

The term “fluoropolymer” refers to a homopolymer or a copolymer derivedfrom interpolymerized units of at least one of the following monomers:tetrafluoroethylene (TFE), vinylidene fluoride (VDF), vinyl fluorine(VF), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE),fluoroalkyl vinyl ethers, fluoroalkoxy vinyl ethers, fluorinatedstyrenes, hexafluoropropylene oxide (HFPO), fluorinated siloxanes, orcombinations thereof.

Various exemplary embodiments of the disclosure will now be describedwith particular reference to the Drawings. Exemplary embodiments of thepresent disclosure may take on various modifications and alterationswithout departing from the spirit and scope of the disclosure.Accordingly, it is to be understood that the embodiments of the presentdisclosure are not to be limited to the following described exemplaryembodiments, but are to be controlled by the limitations set forth inthe claims and any equivalents thereof.

A method of making a nanostructured surface on a substrate is disclosedherein. In some embodiments, the substrate can be in the form of a flat,continuous film. In other embodiments, the substrate can be an articlethat has at least part of one surface upon which it is desired to createa nanostructure. The substrate or article can be made of any materialthat can be etched by the methods disclosed herein. For example, thesubstrate can be a (co)polymeric material, an inorganic material, analloy, or a solid solution. In some embodiments, the substrate caninclude a fiber, a glass, a composite, or a microporous membrane.

(Co)polymeric materials include thermoplastics and thermosettingplastics. Typical thermoplastics include, but are not limited to,polyethylene terephthalate (PET), polystyrene, acrylonitrile butadienestyrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate,polyacrylates, thermoplastic polyurethanes, polyvinyl acetate,polyamide, polyimide, polypropylene, polyester, polyethylene,poly(methylmethacrylate), polyethylene naphthalate, polystyreneacrylonitrile, triacetate cellulose, nylon, silicone-polyoxamidepolymers, fluoropolymers, cyclic olefin copolymers, and thermoplasticelastomers. Suitable thermosets include, but are not limited to, allylresins, epoxies, thermosetting polyurethanes, and silicones orpolysiloxanes. These resins can be formed from the reaction product ofpolymerizable compositions comprising at least one oligomeric urethane(meth)acrylate. Typically, the oligomeric urethane (meth)acrylate is amulti(meth)acrylate. The term “(meth)acrylate” is used to designateesters of acrylic and methacrylic acids, and “multi(meth)acrylate”designates a molecule containing more than one (meth)acrylate group, asopposed to “poly(meth)acrylate” which commonly designates (meth)acrylatepolymers. Most often, the multi(meth)acrylate is a di(meth)acrylate, butit is also contemplated to employ tri(meth)acrylates,tetra(meth)acrylates and so on.

Oligomeric urethane multi(meth)acrylates may be obtained commercially,for example from Sartomer under the trade designation “PHOTOMER 6000Series”, such as “PHOTOMER 6010” and “PHOTOMER 6020”, and also under thetrade designation “CN 900 Series”, such as “CN966B85”, “CN964” and“CN972”. Oligomeric urethane (meth)acrylates are also available fromSurface Specialties, such as available under the trade designations“EBECRYL 8402”, “EBECRYL 8807” and “EBECRYL 4827”. Oligomeric urethane(meth)acrylates may also be prepared by the initial reaction of analkylene or aromatic diisocyanate of the formula OCN—R₃—NCO with apolyol.

Most often, the polyol is a diol of the formula HO—R₄—OH wherein R₃ is aC₂₋₁₀₀ alkylene or an arylene group and R₄ is a C₂₋₁₀₀ alkylene group.The intermediate product is then a urethane diol diisocyanate, whichsubsequently can undergo reaction with a hydroxyalkyl (meth)acrylate.Suitable diisocyanates include 2,2,4-trimethylhexylene diisocyanate andtoluene diisocyanate. Alkylene diisocyanates are generally useful. Acompound of this type may be prepared from 2,2,4-trimethylhexylenediisocyanate, poly(caprolactone)diol and 2-hydroxyethyl methacrylate. Inat least some cases, the urethane (meth)acrylate can be aliphatic. Alsoincluded can be (meth)acrylate esters having other functionality.Compounds of this type are exemplified by the 2-(N-butylcarbamyl)ethyl(meth)acrylates, 2,4-dichlorophenyl acrylate, 2,4,6-tribromophenylacrylate, tribromophenoxylethyl acrylate, t-butylphenyl acrylate, phenylacrylate, phenyl thioacrylate, phenylthioethyl acrylate, alkoxylatedphenyl acrylate, isobornyl acrylate and phenoxyethyl acrylate. Thereaction product of tetrabromobisphenol A diepoxide and (meth)acrylicacid is also suitable.

The other monomer may also be a monomeric N-substituted orN,N-disubstituted (meth)acrylamide, especially an acrylamide. Theseinclude N-alkylacrylamides and N,N-dialkylacrylamides, especially thosecontaining C₁₋₄ alkyl groups. Examples are N-isopropylacrylamide,N-t-butylacrylamide, N,N-dimethylacrylamide and N,N-diethylacrylamide.

The other monomer may further be a polyol multi(meth)acrylate. Suchcompounds are typically prepared from aliphatic diols, triols, and/ortetraols containing 2-10 carbon atoms. Examples of suitablepoly(meth)acrylates are ethylene glycol diacrylate, 1,6-hexanedioldiacrylate, 2-ethyl-2-hydroxymethyl-1,3-propanediol triacylate(trimethylolpropane triacrylate), di(trimethylolpropane) tetraacrylate,pentaerythritol tetraacrylate, the corresponding methacrylates and the(meth)acrylates of alkoxylated (usually ethoxylated) derivatives of saidpolyols.

Monomers having two or more (ethylenically unsaturated groups can serveas a crosslinker. Styrenic compounds suitable for use as the othermonomer include styrene, dichlorostyrene, 2,4,6-trichlorostyrene,2,4,6-tribromostyrene, 4-methylstyrene and 4-phenoxystyrene.Ethylenically unsaturated nitrogen heterocycles includeN-vinylpyrrolidone and vinylpyridine.

Useful inorganic materials for the substrate include, for example,glasses, metals, metal oxides, and ceramics. In some embodiments,inorganic materials include silicon, silicon oxide, germanium, zirconia,vanadium pentoxide, molybdenum, copper, titanium, titanium dioxide,gallium arsenide, diamond, aluminum oxide, silicon nitride, indium tinoxide, and tungsten carbide.

The provided method prepares articles that in some embodiments have thedeposited species is present over all of the etched surface. In some ofthese embodiments, the concentration of the deposited species variescontinuously according to the depth from the exposed surface. Theexposed surface of the substrate can be a flat side of a (co)polymericsheet or web. Alternatively, the exposed surface can be any surface ofan article that can have enhanced optical, mechanical, electrical,adhesive, or catalytic properties by the production of nanostructuresthereon.

The deposited species is the reaction product of plasma chemical vapordeposition derived from the first gaseous species. The first gaseousspecies may be a compound selected from organosilicon compounds, metalalkyls, metal isopropoxides, metal acetylacetonates and metal halides.Typically, the organosilicon compounds can include tetramethylsilane,trimethylsilane, hexamethyldisiloxane, tetraethylorthosilicate, or apolyhedral oligomeric silsesquioxane. Useful metal alkyls can comprisetrimethylaluminum, tributylaluminum, tributyltin, or tetramethylgallium. Useful metal isopropoxides can comprise titanium isopropoxide,or zirconium isopropoxide. Useful metal acetylacetonates can compriseplatinum acetylacetonates, or copper acetylacetonate. Useful metalhalides can comprise titanium tetrachloride, or silicon tetrachloride. Asurprising aspect of the disclosure is that the etching and thedeposition can be performed simultaneously, that the etching by thesecond gaseous species does not also remove the deposition by the firstgaseous species.

Plasma chemical vapor deposition (or plasma-enhanced chemical vapordeposition) is a process by which plasmas, typically generated byradio-frequency discharge, are formed in the space between twoelectrodes when that space is filled with a reacting gas or gases.Plasma chemical vapor deposition is done under vacuum to reduce sidereactions from unwanted species being present in the reacting chamber.The reacting gas or gases typically deposit thin solid films on asubstrate. In the provided method, the first gaseous species forms alayer on the substrate using plasma chemical vapor depositionsimultaneously with the etching. In some embodiments, the etchingresults in a surface with areas of random depth in the direction normalto the original exposed surface. The provided method includes etchingportions of the major surface to form a nanostructure on the substratewhile simultaneously depositing a layer on the etched surface.Typically, reactive ion etching is used for the etching.

In one embodiment, the provided method can be carried out using acontinuous roll-to-roll process referred to as “cylindrical reactive ionetching” (cylindrical RIE). Cylindrical RIE utilizes a rotatingcylindrical electrode to provide etched nanostructures on the surface ofa substrate or article. In many convenient embodiments, the etchingresults nanostructures etched to different depths from the originalsurface. In general, cylindrical RIE can be described as follows. Arotatable cylindrical electrode (“drum electrode”) powered byradio-frequency (RF) and a grounded counter-electrode are providedinside a vacuum vessel. The counter-electrode can comprise the vacuumvessel itself. An etchant gas is fed into the vacuum vessel, and aplasma is ignited and sustained between the drum electrode and thegrounded counter-electrode.

A continuous substrate comprising a random, discontinuous masking layercan then be wrapped around the circumference of the drum and thesubstrate can be etched in the direction normal to the plane of thesubstrate. The exposure time of the substrate can be controlled toobtain a predetermined etch depth of the resulting nanostructure. Theprocess can be carried out at an operating pressure of approximately 10mTorr. Cylindrical RIE is disclosed, for example, in PCT Pat. App. No.US2009/069662 (David et al.).

In another aspect, an article is provided that is made by the methoddescribed herein. FIGS. 1a and 1b are sequential schematic views of anembodiment of an article made by the provided method. FIG. 1a is aschematic illustration of substrate 101 having major surface 103. FIG.1b is an illustration of the same article shown in FIG. 1a after havingbeen treated with a plasma including the first and the second gaseousspecies. The second gaseous species has etched major surface 103 (theoriginal surface shown in phantom), leaving microstructures 105 ofdiverse height and aspect ratio. At least portions of the etched surface103 have a layer 107 deposited upon them via the first gaseous species,typically the highest parts of the nanostructures 105. In manyconvenient embodiments, the layer of the deposited species is presentover all of the etched surface with a concentration that variescontinuously according to the depth from the major surface 103.

FIGS. 2 and 3 illustrate a cylindrical RIE apparatus that is useful forthe method of the disclosure. A common element for plasma creation andion acceleration is generally indicated as 210. This RIE apparatus 210includes a support structure 212, a housing 214 including a front panel216 of one or more doors 218, side walls 220 and a back plate 222defining an inner chamber 224 therein divided into one or morecompartments, a drum 226 rotatably affixed within the chamber, aplurality of reel mechanisms rotatably affixed within the chamber andreferred to generally as 228, drive mechanism 237 for rotatably drivingdrum 226, idler rollers 232 rotatably affixed within the chamber, andvacuum pump 234 fluidly connected to the chamber.

Support structure 212 is any means known in the art for supportinghousing 214 in a desired configuration, a vertically upright manner inthe present case. As shown in FIGS. 2 and 3, housing 214 can be atwo-part housing as described below in more detail. In this embodiment,support structure 212 includes cross supports 240 attached to each sideof the two-part housing for supporting apparatus 210. Specifically,cross supports 240 include both wheels 242 and adjustable feet 244 formoving and supporting, respectively, apparatus 210. In the embodimentshown in FIGS. 2 and 3, cross supports 240 are attached to each side ofhousing 214 through attachment supports 246. Specifically, crosssupports 240 are connected to one of side walls 220, namely the bottomside wall, via attachment supports 246, while cross supports 240 on theother side of housing 214 are connected to back plate 222 by attachmentsupports 246. An additional crossbar 247 is supplied between crosssupports 240 on the right-hand side of apparatus 210 as shown in FIG. 2.This can provide additional structural reinforcement.

Housing 214 can be any means of providing a controlled environment thatis capable of evacuation, containment of gas introduced afterevacuation, plasma creation from the gas, ion acceleration, and etching.In the embodiment shown in FIGS. 2 and 3, housing 214 has outer wallsthat include front panel 216, four side walls 220, and a back plate 222.The outer walls define a box with a hollow interior, denoted as chamber224. Side walls 220 and back plate 222 are fastened together, in anymanner known in the art, to rigidly secure side walls 220 and back plate222 to one another in a manner sufficient to allow for evacuation ofchamber 224, containment of a fluid for plasma creation, plasmacreation, ion acceleration, and etching. Front panel 216 is not fixedlysecured so as to provide access to chamber 224 to load and unloadsubstrate materials and to perform maintenance. Front panel 216 isdivided into two plates connected via hinges 250 (or an equivalentconnection means) to one of side walls 220 to define a pair of doors218. These doors seal to the edge of side walls 220, preferably throughthe use of a vacuum seal (for example, an O-ring). Locking mechanisms252 selectively secure doors 218 to side walls 220 and can be anymechanism capable of doors 218 to walls 220 in a manner allowing forevacuation of chamber 224, storage of a fluid for plasma creation,plasma creation, ion acceleration, and etching.

In one embodiment, chamber 224 is divided by a divider wall 254 into twocompartments 256 and 258. A passage or hole 260 in wall 254 provides forpassage of fluids or substrate between compartments. Alternatively, thechamber can be only one compartment or three or more compartments.Preferably, the chamber is only one compartment.

Housing 214 includes a plurality of view ports 262 with high pressure,clear (co)polymeric plates 264 sealably covering ports 262 to allow forviewing of the etching process occurring therein. Housing 214 alsoincludes a plurality of sensor ports 266 in which various sensors (forexample, temperature, pressure, etc.) can be secured. Housing 214further includes inlet ports 268 providing for conduit connectionthrough which fluid can be introduced into chamber 224 as needed.Housing 214 also includes pump ports 270 and 272 that allow gases andliquids to be pumped or otherwise evacuated from chamber 224.

Pump 234 is shown suspended from one of sides 220, typically the bottom(as shown in FIG. 3). Pump 234 can be, for example, a turbo-molecularpump fluidly connected to the controlled environment within housing 214.Other pumps, such as diffusion pumps or cryopumps, can be used toevacuate lower chamber 258 and to maintain operating pressure therein.The process pressure during the etching step is preferably chosen to bebetween about 1 mTorr and about 20 mTorr (more preferably, between about5 mTorr and about 10 mTorr) to provide anisotropic etching. Slidingvalve 273 is positioned along this fluid connection and can selectivelyintersect or block fluid communication between pump 234 and the interiorof housing 214. Sliding valve 273 is movable over pump port 262 so thatpump port 262 can be fully open, partially open, or closed with respectto fluid communication with pump 234.

Drum 226 typically is a cylindrical electrode 280 with an annularsurface 282 and two planar end surfaces 284. The electrode can be madeof any electrically conductive material and preferably is a metal suchas, for example, aluminum, copper, steel, stainless steel, silver,chromium or an alloy of any one or more of the foregoing. Preferably,the electrode is aluminum, because of the ease of fabrication, lowsputter yield, and low costs.

Drum 226 is further constructed to include non-coated, conductiveregions that allow an electric field to permeate outward as well asnon-conductive, insulative regions for preventing electric fieldpermeation and thus for limiting film coating to the non-insulated orconductive portions of the electrode. The electrically non-conductivematerial typically is an insulator, such as a (co)polymer (for example,polytetrafluoroethylene). Various embodiments that fulfill thiselectrically non-conductive purpose so as to provide only a smallchannel, typically the width of the substrate to be coated, as aconductive area can be envisioned by one of ordinary skill in the art.

FIG. 2 shows an embodiment of drum 226 where annular surface 282 and endsurfaces 284 of drum 226 are coated with an electrically non-conductiveor insulative material, except for annular channel 290 in annularsurface 282 which remains uncoated and thus electrically conductive. Inaddition, a pair of dark space shields 286 and 288 cover the insulativematerial on annular surface 282, and, in some embodiments, cover endsurfaces 284. The insulative material limits the surface area of theelectrode along which plasma creation and negative biasing may occur.However, since the insulative materials sometimes can become fouled bythe ion bombardment, dark space shields 286 and 288 can cover part orall of the insulated material. These dark space shields may be made froma metal such as aluminum but do not act as conductive agents becausethey are separated from the electrode by means of an insulating material(not shown). This allows confinement of the plasma to the electrodearea.

Another embodiment of drum 226 is shown in FIGS. 4A and 4B where drum226 includes a pair of insulative rings 285 and 287 affixed to annularsurface 282 of drum 226. In some embodiments, insulative ring 287 is acap which acts to also cover end surface 284. Bolts 292 secure supportmeans 294, embodied as a flat plate or strap, to back plate 222. Bolts292 and support means 294 can assist in supporting the various parts ofdrum 226. The pair of insulative rings 285 and 287, once affixed toannular surface 282, define an exposed electrode portion embodied aschannel 290.

In any case, electrode 280 is covered in some manner by an insulativematerial in all areas except where the substrate contacts the electrode(that is, touching or within the plasma dark space limit of theelectrode (for example, about 3 mm)). This defines an exposed electrodeportion that can be in intimate contact with the substrate. Theremainder of the electrode is covered by an insulative material. Whenthe electrode is powered and the electrode becomes negatively biasedwith respect to the resultant plasma, this relatively thick insulativematerial prevents etching on the surfaces it covers. As a result,etching is limited to the uncovered area (that is, that which is notcovered with insulative material, channel 290), which preferably iscovered by relatively thin substrate material.

Referring to FIGS. 2 and 3, drum 226 is rotatably affixed to back plate222 through a ferrofluidic feedthrough and rotary union 238 (or anequivalent mechanism) affixed within a hole in back plate 222. Theferrofluidic feedthrough and rotary union provide separate fluid andelectrical connection from a standard coolant fluid conduit andelectrical wire to hollow coolant passages and the conductive electrode,respectively, of rotatable drum 226 during rotation while retaining avacuum seal. The rotary union also supplies the necessary force torotate the drum, which force is supplied from any drive means such as abrushless DC servo motor. However, connection of drum 226 to back plate222 and the conduit and wire may be performed by any means capable ofsupplying such a connection and is not limited to a ferrofluidicfeedthrough and a rotary union. One example of such a ferrofluidicfeedthrough and rotary union is a two-inch (about 5 cm) inner diameterhollow shaft feedthrough made by Ferrofluidics Co. (Nashua, N.H.).

Drum 226 is rotatably driven by drive mechanism 237, which can be anymechanical and/or electrical system capable of translating rotationalmotion to drum 226. In the embodiment shown in FIG. 3, drive mechanism237 includes motor 233 with a drive shaft terminating in drive pulley231 that is mechanically connected to a driven pulley 239 rigidlyconnected to drum 226. Belt 235 (or equivalent structure) translatesrotational motion from drive pulley 231 to driven pulley 239.

The plurality of reel mechanisms 228 are rotatably affixed to back plate222. The plurality of reel mechanisms 228 includes a substrate reelmechanism with a pair of substrate spools 228A and 228B, and, in someembodiments, also can include a spacing web reel mechanism with a pairof spacing web spools 228C and 228D, and masking web reel mechanism witha pair of masking web spools 228E and 228F, where each pair includes onedelivery and one take-up spool. As is apparent from FIG. 3, at leasteach take-up spool 228B, 228D, and 228F includes a drive mechanism 227mechanically connected thereto such as a standard motor as describedbelow for supplying a rotational force that selectively rotates the reelas needed during etching. In addition, each spool 228A, 228C, and 228Ein select embodiments includes a tensioner for supplying tautness to thewebs and/or a drive mechanism 229.

Each reel mechanism includes a delivery and a take-up spool which may bein the same or a different compartment from each other, which in turnmay or may not be the same compartment the electrode is in. Each spoolis of a standard construction with an axial rod and a rim radiallyextending from each end defining a groove in which an elongated member,in this case a substrate or web, is wrapped or wound. Each spool issecurably affixed to a rotatable stem sealably extending through backplate 222. In the case of spools to be driven, the stem is mechanicallyconnected to a motor 227 (for example, a brushless DC servo motor). Inthe case of non-driven spools, the spool is merely coupled in arotatable manner through a coupling 229 to back plate 222 and mayinclude a tension mechanism to prevent slack.

RIE apparatus 210 also includes idler rollers 232 rotatably affixedwithin the chamber and pump 234 fluidly connected to the chamber. Theidler rollers guide the substrate from the substrate spool 228A tochannel 290 on drum 226 and from channel 290 to take-up substrate spool228B. In addition, where spacing webs and masking webs are used, idlerrollers 232 guide these webs and the substrate from substrate spool 228Aand masking web spool 228E to channel 290 and from channel 290 totake-up substrate spool 228B and take-up masking web spool 228F,respectively.

RIE apparatus 210 further includes a temperature control system forsupplying temperature controlling fluid to electrode 280 viaferrofluidic feedthrough 238. The temperature control system may beprovided on apparatus 210 or alternatively may be provided from aseparate system and pumped to apparatus 210 via conduits so long as thetemperature control fluid is in fluid connection with passages withinelectrode 280. The temperature control system may heat or cool electrode280 as is needed to supply an electrode of the proper temperature foretching. In a preferred embodiment, the temperature control system is acoolant system using a coolant such as, for example, water, ethyleneglycol, chloro fluorocarbons, hydrofluoroethers, and liquefied gases(for example, liquid nitrogen).

RIE apparatus 210 also includes an evacuation pump fluidly connected toevacuation port(s) 270. This pump may be any vacuum pump, such as aRoots blower, a turbo molecular pump, a diffusion pump, or a cryopump,capable of evacuating the chamber. In addition, this pump may beassisted or backed up by a mechanical pump. The evacuation pump may beprovided on apparatus 210 or alternatively may be provided as a separatesystem and fluidly connected to the chamber.

RIE apparatus 210 also includes a fluid feeder, preferably in the formof a mass flow controller that regulates the fluid used to create thethin film, the fluid being pumped into the chamber after evacuationthereof. The feeder may be provided on apparatus 210 or alternativelymay be provided as a separate system and fluidly connected to thechamber. The feeder supplies fluid in the proper volumetric rate or massflow rate to the chamber during etching. The etching gases can include,for example, oxygen, argon, chlorine, fluorine, carbon tetrafluoride,carbontetrachloride, perfluoromethane, perfluoroethane,perfluoropropane, nitrogen trifluoride, sulfur hexafluoride, methane,and the like. Mixtures of gases may be used advantageously to enhancethe etching process.

Additional gases may be used for enhancing the etching rate ofhydrocarbons or for the etching of non-hydrocarbon materials. Forexample, fluorine containing gases such as perfluoromethane,perfluoroethane, perfluoropropane, sulfurhexafluoride, nitrogentrifluoride, and the like can be added to oxygen or introduced bythemselves to etch materials such as SiO₂, tungsten carbide, siliconnitride, amorphous silicon, and the like. Chlorine-containing gases canlikewise be added for the etching of materials such as aluminum, sulfur,boron carbide, and the like. Hydrocarbon gases such as methane can beused for the etching of materials such as gallium arsenide, gallium,indium, and the like. Inert gases, particularly heavy gases such asargon can be added to enhance the anisotropic etching process.

RIE apparatus 210 also includes a power source electrically connected toelectrode 280 via electrical terminal 230. The power source may beprovided on apparatus 210 or alternatively may be provided on a separatesystem and electrically connected to the electrode via electricalterminal (as shown in FIG. 3). In any case, the power source is anypower generation or transmission system capable of supplying sufficientpower. (See discussion infra.)

Although a variety of power sources are possible, RF power is preferred.This is because the frequency is high enough to form a self bias on anappropriately configured powered electrode but not high enough to createstanding waves in the resulting plasma. RF power is scalable for highoutput (wide webs or substrates, rapid web speed). When RF power isused, the negative bias on the electrode is a negative self bias, thatis, no separate power source need be used to induce the negative bias onthe electrode. Because RF power is preferred, the remainder of thisdiscussion will focus exclusively thereon.

The RF power source powers electrode 280 with a frequency in the rangeof 0.01 to 50 MHz preferably 13.56 MHz or any whole number (for example,1, 2, or 3) multiple thereof. This RF power as supplied to electrode 280creates a plasma from the gas within the chamber. The RF power sourcecan be an RF generator such as a 13.56 MHz oscillator connected to theelectrode via a network that acts to match the impedance of the powersupply with that of the transmission line (which is usually 50 ohmsresistive) so as to effectively transmit RF power through a coaxialtransmission line.

Upon application of RF power to the electrode, the plasma isestablished. In an 15 RF plasma the powered electrode becomes negativelybiased relative to the plasma. This bias is generally in the range of500 to 1400 volts. This biasing causes ions within the plasma toaccelerate toward electrode 280. Accelerating ions etch the article incontact with electrode 280 as is described in more detail below.

In operation, a full spool of substrate upon which etching is desired isinserted over the stem as spool 228A. Access to these spools is providedthrough lower door 218 since, in FIGS. 2 and 3, the spools are locatedin lower compartment 258 while etching occurs in upper compartment 256.In addition, an empty spool is fastened opposite the substrate holdingspool as spool 228B so as to function as the take-up spool after etchinghas occurred. If a spacer web is desired to cushion the substrate duringwinding or un-winding, spacer web delivery and/or take-up spool can beprovided as spools 228C and 228D (although the location of the spools inthe particular locations shown in the figures is not critical).Similarly, if etching is desired in a pattern or otherwise partialmanner, a masking web can be positioned on an input spool as spool 228Eand an empty spool is positioned as a take-up spool as spool 228F.

After all of the spools with and without substrates or webs arepositioned, the substrate on which etching is to occur (and any maskingweb to travel therewith around the electrode) are woven or otherwisepulled through the system to the take-up reels. Spacer webs generallyare not woven through the system and instead separate from the substratejust before this step and/or are provided just after this step. Thesubstrate is specifically wrapped around electrode 280 in channel 290thereby covering the exposed electrode portion. The substrate issufficiently taut to remain in contact with the electrode and to movewith the electrode as the electrode rotates so a length of substrate isalways in contact with the electrode for etching. This allows thesubstrate to be etched in a continuous process from one end of a roll tothe other. The substrate is in position for etching and lower door 218is sealed closed.

Chamber 224 is evacuated to remove all air and other impurities. Once anetchant gas mixture is pumped into the evacuated chamber, the apparatusis ready to begin the process of etching. The RF power source isactivated to provide an RF electric field to electrode 80. This RFelectric field causes the gas to become ionized, resulting in theformation of a plasma with ions therein. This is specifically producedusing a 13.56 MHz oscillator, although other RF sources and frequencyranges may be used. The power density of the RF power of the etchingprocess is preferably in the range of about 0.1 to about 1.0 watts/cm³(preferably, about 0.2 to about 0.4 watts/cm³).

Once the plasma has been created, a negative DC bias voltage is createdon electrode 280 by continuing to power the electrode with RF power.This bias causes ions to accelerate toward annular channel 290 ofelectrode 280 (the remainder of the electrode is either insulated orshielded). The ions selectively etch the substrate material (versus themask material) in the length of substrate in contact with channel 290 ofelectrode 280 causing anisotropic etching of the substrate material onthat length of substrate.

For continuous etching, the take-up spools are driven so as to pull thesubstrate and any masking webs through the upper compartment 254 andover electrode 280 so that etching of the matrix occurs on any unmaskedsubstrate portions in contact with annular channel 290. The substrate isthus pulled through the upper compartment continuously while acontinuous RF field is placed on the electrode and sufficient reactivegas is present within the chamber. The result is a continuous etching onan elongated substrate, and substantially only on the substrate. Etchingdoes not occur on the insulated portions of the electrode nor doesetching occur elsewhere in the chamber. To prevent the active power fedto the plasma from being dissipated in the end plates of the cylindricalelectrode, grounded dark space shields 286 and 288 can be used. Darkspace shields 286 and 288 can be of any shape, size, and material thatis conducive to the reduction of potential fouling. In the embodimentshown in FIGS. 2 and 3, dark space shields 286 and 288 are metal ringsthat fit over drum 226 and the insulation thereon. Dark space shields286 and 288 do not bias due to the insulating material that covers drum226 in the areas where dark space shields 286 and 288 contact drum 226.The dark space shields in this ring-like embodiment further include tabson each end thereof extending away from drum 226 in a non-annularmanner. These tabs can assist in aligning the substrate within channel290.

Typically, the temperature control system pumps fluid through electrode280 throughout the process to keep the electrode at a desiredtemperature. Typically, this involves cooling the electrode with acoolant as described above, although heating in some cases may bedesirable. In addition, since the substrate is in direct contact withthe electrode, heat transfer from the plasma to the substrate is managedthrough this cooling system, thereby allowing the coating of temperaturesensitive films such as polyethyleneterephthalate, polyethylenenaphthalate, and the like. After completion of the etching process, thespools can be removed from shafts supporting them on the wall. Thenanostructured substrate is on spool 228B and is ready for use.

The surface of the substrate, itself, may be microstructured. Forexample, a thin, random, discontinuous masking layer can be applied to amajor surface of a substrate with a v-groove microstructured surface byplasma chemical vapor deposition to form nanostructures on v-groovemicrostructured surface. Alternatively, a microstructured article suchas Fresnel lens or a microstructured article comprising microreplicatedposts or columns comprising nanodispersed phases can be also treated byplasma etching to form nanostructures on microstructures.

The nanostructured surface made by the method of the disclosure can havea nanostructured anisotropic surface. The nanostructured anisotropicsurface typically can comprise nanoscale features having a height towidth ratio or about 2:1 or greater, preferably about 5:1 or greater. Insome embodiments, the height to width ratio can even be 50:1 or greater,100:1 or greater, or 200:1 or greater. The nanostructured anisotropicsurface can comprise nanofeatures such as, for example, nano-pillars ornano-columns, or continuous nano-walls comprising nano-pillars ornano-columns. Typically, the nanofeatures have steep side walls that aresubstantially perpendicular to the substrate.

In some embodiments, the majority of the nanofeatures can be capped withmask material. The concentration of the mask material at the surface canbe from about 5 weight % to about 90 weight % or from about 10 weight %to about 75 weight %.

In certain embodiments, the substrate may comprise materials for staticdissipation in order to minimize attraction of dirt and particulate andthus maintain surface quality. Suitable materials for static dissipationinclude, for example, STAT-RITE polymers such X-5091, M-809, S-5530,S-400, S-403, and S-680 (available from Lubrizol, Wickliffe, Ohio);3,4-polyethylenedioxythiophene-polystyrenesulfonate (PEDOT/PSS)(available from H.C. Starck, Cincinnati, Ohio); polyanaline;polythiophene; and PELESTAT NC6321 and NC7530 antistatic additives(available from Tomen America Inc., New York, N.Y.).

The nanostructured articles made by the provided method can exhibit oneor more desirable properties such as antireflective properties, lightabsorbing properties, antifogging properties, improved adhesion anddurability. For example, in some embodiments, the surface reflectivityof the nanostructured anisotropic surface is about 50% or less than thesurface reflectivity of an untreated surface. As used herein withrespect to comparison of surface properties, the term “untreatedsurface” means the surface of an article comprising the same matrixmaterial and the same nanodispersed phase (as the nanostructured surfaceof the disclosure to which it is being compared) but without ananostructured anisotropic surface. In some embodiments, the percentreflection of the nanostructured anisotropic surface can be less thanabout 2% (typically, less than about 1%) as measured using the“Measurement of Average % Reflection” method described in the Examplesection below. Likewise, in some embodiments, the percent transmissionof the nanostructured anisotropic surface can be about 2% or more thanthe percent transmission of an untreated surface as measured using the“Measurement of Average % Transmission” method described in the Examplesection below.

In other embodiments, the nanostructured anisotropic surface can have awater contact angle of less than about 20°, less than about 15°, or evenless than about 10° as measured using the “Water Contact AngleMeasurement” method described in the Example section below. In stillother embodiments, the nanostructured anisotropic surface can absorbabout 2% or more light than an untreated surface. In yet otherembodiments of the disclosure, the nanostructured anisotropic surfacecan have a pencil hardness greater than about 2H (typically, greaterthan about 4H) as determined according to ASTM D-3363-05. In otherembodiments, an article is provided that can be made in a continuousmanner by the provided method so that the percentage of light (measuredat 450 nm) transmitted through the localized nanostructured surface thatis deflected more than 2.5 degrees from the direction of incoming beamis less than 2.0%, typically less than 1.0%, and more typically lessthan 0.5%.

Some embodiments of the disclosure further comprise a layer or coatingcomprising, for example, ink, encapsulant, adhesive, or metal attachedto the nanostructured anisotropic surface. The layer or coating can haveimproved adhesion to the nanostructured anisotropic surface of thedisclosure than to an untreated surface.

The nanostructured articles made by the method of the disclosure areuseful for numerous applications including, for example, displayapplications (for example, liquid crystal displays (LCD), light emittingdiode (LED) displays, or plasma displays); light extraction;electromagnetic interference (EMI) shielding, ophthalmic lenses; faceshielding lenses or films; window films; antireflection for constructionapplications, construction applications or traffic signs; and the like.The nanostructured articles are also useful for solar applications suchas solar films and Fresnel lenses. They can be used as the front surfaceand/or secondary surface of solar thermal hot liquid/air heat panels orany solar energy absorbing device; for solar thermal absorbing surfaceshaving micro- or macro-columns with additional nanoscale surfacestructure; for the front surface of flexible solar photovoltaic cellsmade with amorphous silica photovoltaic cells or CIGS photovoltaiccells; and for the front surface of a film applied on top of flexiblephotovoltaic cells.

In another embodiment of the disclosure, the mask material dispersed onthe substrate can be etched away using plasma to form a nanostructured(or nanoporous) surface. This method can be carried out usingcylindrical RIE essentially as described above, but using etchingselectivity to favor etching the dispersed material rather than thesubstrate (that is, by selecting gases that etch dispersed phasematerial rather than the substrate material).

Fluoropolymeric substrates are notoriously difficult to join to adjacentlayers by, e.g. adhering, laminating, and compression molding. Filmforming materials coated onto such substrates are also show unusuallylow attachment. Common expedients for increasing attachment tosubstrates, such as flame or corona treatment, are typically ineffectivewhen applied to fluoropolymeric substrates. It has been found thatproviding fluoropolymeric substrates with a least one nanostructuredsurface formed via the techniques of this disclosure allow much greaterattachment of adjacent layers. Referring now to FIG. 9, a side view of amultilayered laminate 300 including a fluoropolymer substrate 302provided with a nanostructure 304, joined with an adjacent film 306.Laminates such as the one illustrated can be obtained by, e.g.,laminating the nanostructured surface with a film, by compressionmolding a film against the nanostructured surface, and by coating afilm-forming material onto the nanostructured surface. Of particularinterest, useful laminates can include pressure sensitive adhesivescontacting the nanostructured surface. For example, useful laminates maybe obtained by application of a pressure sensitive adhesive compositionfrom a transfer liner at room temperature without any otherpretreatment. Additionally, they can be obtained by extrusion coating ofhot melt adhesives, solvent coating of solvent-borne adhesives, or slotcoating of liquid adhesives. This is not possible with the traditionaltreatment methods for fluoropolymer films.

Preferred fluoropolymers include PTFE polymers such as S-PTFE andE-PTFE. They also include fluorothermoplastics such as ECTFE, EFEP,ETFE, FEP, HTE, PCTFE, PFA, PVF, PVDF, THV, and Teflon® AF polymers.Also included are fluoroelastomers such as FKM, PFE, and LTFE.

Referring now to FIG. 10, a cross section view of a multilayeredlaminate 400, including a fluoropolymer substrate 402 provided with ananostructure 404, joined with an adhesive layer 406 is illustrated.Adhesive layer 406 is in turn adhered to one surface of a material 408needing to be protected. Since in the illustrated embodiment theexterior facing surface 410 of fluoropolymer substrate 402 has not beenprovided with a nanostructure, it retains its chemical and adhesionresistance. If the adhesive layer 406 is a pressure sensitive adhesive,multilayered laminate 400 could be suited for use as, e.g. a graffitiprotection film for architectural use. Alternatively, if the adhesivelayer 406 is an epoxy adhesive, multilayered laminate 400 could besuited for use as, e.g. a protective laminate for the inside of achemical reactor. Alternatively, if the adhesive layer 406 is anoptically clear adhesive with a UV absorbing quality, multilayeredlaminate 400 could be suited for use as, e.g. a solar film useful forwindow film or protecting photovoltaic cells. In some embodiments wherephotovoltaic cells are to be protected an encapsulant layer such as EVAmay be positioned against the nanostructured surface, or interposedbetween the photovoltaic cell and an adhesive layer positioned againstthe nanostructured surface.

Referring now to FIG. 11, a cross section view of a multilayeredlaminate 500 including a fluoropolymer substrate 502 provided with ananostructure 504 a and 504 b on each of two major surfaces, each of thenanostructures 504 a and 504 b joined with an adhesive layer 506 a and506 b, each adhesive layer 506 a and 506 b in turn adhered to onesurface of a materials 508 a and 508 b needing to be joined. If forexample materials 508 a and 508 b are glass, the combined structurecould be well suited as a glazing laminate.

The operation of various embodiments of the present disclosure will befurther described with regard to the following detailed Examples.

Examples

These Examples are merely for illustrative purposes and are not meant tobe overly limiting on the scope of the appended claims. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof the present disclosure are approximations, the numerical values setforth in the specific examples are reported as precisely as possible.Any numerical value, however, inherently contains certain errorsnecessarily resulting from the standard deviation found in theirrespective testing measurements. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques.

Unless otherwise noted, all parts, percentages, ratios, etc. in theExamples and the rest of the specification are provided on the basis ofweight. Solvents and other reagents used may be obtained fromSigma-Aldrich Chemical Company (Milwaukee, Wis.) unless otherwise noted.

The provided nanostructures and methods described herein were obtainedby using a homebuilt plasma treatment system described in detail in U.S.Pat. No. 5,888,594 (David et al.) with some modifications and isillustrated in FIGS. 2, 3, and 4 a and 4 b. The width of the drumelectrode was increased to 42.5 inches (108 cm) and the separationbetween the two compartments within the plasma system was removed sothat all the pumping was carried out by means of the turbo-molecularpump and thus operating at a much lower operating pressure than isconventionally done with plasma processing.

Measurement of Reflectance (Average Reflection %)

The Reflectance (Average Reflection % or % R) of the plasma treatedsurface was measured using BYK Gardiner color guide sphere. One sampleof each film was prepared by applying Yamato Black Vinyl Tape #200-38(obtained from Yamato International Corporation, Woodhaven, Mich.) tothe backside of the sample. A Clear glass slide of which transmissionand reflection from both sides were predetermined was utilized toestablish the % reflection from the black tape. The black tape waslaminated to the backside of the sample using a roller to ensure therewere no air bubbles trapped between the black tape and the sample. Tomeasure the front surface total Reflectance (% R, specular and diffuse)by an integrating sphere detector, the sample was placed in the machineso that the non-tape side was against the aperture. The Reflectance (%R) was measured at a 10° incident angle and average Reflectance (% R)was calculated by subtracting the Reflectance (% R) of the black tapefor the wavelength range of 400-700 nm.

Measurement of Haze and Transmission

Measurement of Haze and Transmission was carried out with BYK HazeDelta-Gard Plus (from BYK Gardiner, Columbia, Md.) according to ASTMD1003 & D1004.

Measurement of Weathering

3-1 Weathering

The test panels with the adhered films were exposed to the followingconditions per ASTM G155, Cycle 1: Duration 2000 hours, Xenon Arc Lamp @0.35 W/m²/nm @340 nm, alternate cycles of 102 minutes Xenon Arc light at63° C. Black Panel Temperature and 18 minutes of combination of XenonArc light and DI water spray, with uncontrolled air temperatures.

4-1 Weathering

The test panels with the adhered films were exposed to the followingconditions per ASTM G154, Cycle 2: Duration 2000 hours, UVB-313Fluorescent UV Lamp @0.71 W/m²/nm @ 310 nm, alternate cycles of 4 hoursUV at 60° C. Black Panel Temperature with 4 hours condensation at 50° C.Black Panel Temperature.

Example 1—Nanostructure Formed on PTFE Substrate Film

A roll of extruded 50 micron thick polytetrafluoroethylene (PTFE) filmwas formed by combining a fine powder of emulsion PTFE resin DYNEONTF-2071” of St. with an extrusion lubricant commercially available as“ISOPAR M” from Exxon Mobil of Irving, Tex., according to therecommended weight percentage for the lubricant. These ingredients weremixed into a paste, and this paste was extruded into a film. This filmwas calendered to a specific film thickness using a series of calendarrolls. The sized film was then run through an extractor where thelubricant was removed. Finally, the green film was run through asintering process in a high temperature oven to fuse the film and bringit to the final thickness.

This PTFE film was mounted within the chamber, the film wrapped aroundthe drum electrode, and secured to the take up roll on the opposite sideof the drum. The un-wind and take-up tensions were maintained at 3pounds (13.3 N). The chamber door was closed and the chamber pumped downto a base pressure of 5×10⁻⁴ Torr. The first gaseous species wastetramethylsilane gas provided at a flow rate of 40 sccm and the secondgaseous species was oxygen provided at a flow rate of 500 sccm. Thepressure during the exposure was around 10 mTorr and plasma was turnedon at a power of 6000 watts while the tape was advanced at a speed of 6ft/min (1.83 m/min). The surface morphology of the PTFE films of wasdetermined by SEM analysis and the results are shown in FIG. 5.

Further, an adhesive tape was formed by coating a 0.0017 inch (0.043 mm)thick layer of silicone pressure sensitive adhesive on the sinteredfilm. The specific silicone adhesive was the one used with the PTFE tapecommercially available as “5490 PTFE tape” from 3M Company of SaintPaul, Minn.

As a control to test the adhesion of this adhesive tape, a control tapewas made by using the same fused film discussed above, and the samesilicone adhesive, but instead of using a plasma treatment according tothe disclosure and the protocol above, the fused film was subjected to atraditional chemical etch using sodium naphthalate commerciallyavailable from Acton Technologies of Pittston, Pa. Both the experimentalexample and the control were subjected to a 90° peel test from stainlesssteel, and both showed a peel strength of 20 oz/in (2.19 N/cm), showingthat the film of Example 1 is practical for use in adhesive tapes.

To learn whether this good adhesion could persist in the face ofweathering, the adhesive tape made according the example was exposed toconditions simulative of weathering. In this case, the control was PTFEtape commercially available as “5490 PTFE tape” from 3M Company. Testpanels were prepared by adhering the Example adhesive tape and thecontrol adhesive tape to stainless steel panels. The steel panels werethen exposed to 2000 hours of weathering generally following theprocedures of ASTM G155. More specifically, there were alternate cyclesof 102 minutes with xenon arc light at 63° C. Black Panel Temperatureand 18 minutes of combination of xenon arc light and DI water spray,with uncontrolled air temperatures. The xenon arc lamp employed provided0.35 W/m²/nm at 340 nm. Adhesive strength and visual observation of anytransfer of adhesive to the steel upon a 90° peel test was assessedafter 200, 500, 1000, and finally 2000 hours. The results are presentedin Table 1 below.

TABLE 1 After After After After 200 Hours 500 Hours 1000 Hours 2000Hours Initial Adhesion Adhesion Adhesion Adhesion Adhesion to SteelTransfer to Steel Transfer to Steel Transfer to Steel Transfer Exampleto Steel (oz/in) (%) (oz/in) (%) (oz/in) (%) (oz/in) (%) No. (oz/in)Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Example 1 32 58  10⁽¹⁾ 56 50⁽¹⁾61  50⁽¹⁾ 56  10⁽¹⁾ Control 29 28 100⁽³⁾ 33 95⁽³⁾ 29 100⁽³⁾ 26 100⁽³⁾⁽¹⁾Cohesive transfer ⁽²⁾Adhesive residue, some edge transfer ofadhesive, and panel discoloration/ghosting ⁽³⁾100% transfer of adhesiveto stainless steel panel with complete breakdown of bond strengthbetween primer and PTFE film

Example 2—Nanostructure Formed on PET Substrate Film

A roll of 125 micron thick polyethylene phthalate (PET) film was mountedwithin the chamber, the film wrapped film rapped around the drumelectrode, and secured to the take up roll on the opposite side of thedrum. The un-wind and take-up tensions were maintained at 3 pounds (13.3N). The chamber door was closed and the chamber pumped down to a basepressure of 5×10⁻⁴ Torr. The first gaseous species washexamethyldisiloxane (HMDSO) vapor provided at three different flowrates as outlined in Table 1 below, and the second gaseous species wasoxygen provided at a flow rate of 500 sccm. The pressure during theexposure was around 10 mTorr and plasma was turned on at a power of 6000watts.

The film was advanced at diverse line speeds as outlined in Table 2below. The Reflectance (% R) of the tape was measured according to theprotocol above at each process condition at three locations: the leftedge of the tape, the right edge of the tape, and the center. Averagevalues were also calculated and presented in Table 2. Then the film wasadhered to adhesive tape having an acrylic pressure sensitive adhesive,commercially available as “MAGIC” Tape 810 from 3M Company, St. Paul,Minn. The values resulting from a 90° peel test are also presented inTable 2 in terms of oz/in.

TABLE 2 Conditions Example HMDSO Line Reflectance (%) Adhesion 90° Peel(oz/in) No. Flow rate (sccm) speed (fpm) left center right average leftcenter right average 2-1 10 4 4.05 3.11 3.51 3.56 4 4 4 4 2-2 10 6 5.003.79 3.45 4.08 4 4 4 4 2-3 10 8 5.87 5.07 4.61 5.18 3 4 5 4 2-4 20 41.48 2.15 2.65 2.09 5 5 5 5 2-5 20 6 1.96 1.07 1.23 1.42 5 5 5 5 2-6 208 3.82 2.67 2.12 2.87 4 4 4 4 2-7 30 4 1.37 2.37 2.50 2.08 5 4 4 4.3 2-830 6 2.05 2.58 1.97 2.20 5 5 5 5 2-9 30 8 3.19 3.52 2.38 3.03 4 4 4 3.7

Example 3—Nanostructure Formed on TAC Substrate Film

A roll of film commercially available as 80 micrometer thick cellulosetriacetate film, commercially available as “IPI TAC” (obtained fromIsland Pyrochemical Industries Corp, Mineola, N.Y., under the tradedesignation “IPI TAC”) was mounted within the chamber, the film wrappedaround the drum electrode, and secured to the take up roll on theopposite side of the drum using adhesive tape. The un-wind and take-uptensions were maintained at 3 pounds (13.3 N). The chamber door wasclosed and the chamber pumped down to a base pressure of 5×10⁻⁴ Torr.

The first gaseous species was hexamethyldisiloxane (HMDSO) vaporprovided at three different flow rates as outlined in Table 2 below, andthe second gaseous species was oxygen provided at a flow rate of 500sccm. The pressure during the exposure was around 10 mTorr and plasmawas turned on at a power of 6000 watts. The tape was advanced at diverseline speeds as outlined in Table 3 below. The Reflectance (% R) of thetape was measured according to the protocol above at each processcondition at three locations: the left edge of the tape, the right edgeof the tape, and the center. Average values were also calculated andpresented in Table 3. Then the film was adhered to adhesive tape havingan acrylic pressure sensitive adhesive, commercially available as“MAGIC” Tape 810 from 3M Company. The values resulting from a 90° peeltest are also presented in Table 3 in terms of oz/in.

TABLE 3 Run Conditions HMDSO Line Adhesion Example Flowrate SpeedReflectance (%) 90° Peel No. (sccm) (fpm) Left Center Right Average(oz/in) 3-1 10 6 1.71 1.64 2.11 1.82 5.0 3-2 10 8 1.13 1.13 1.08 1.115.0 3-3 10 10 1.05 0.94 1.09 1.03 4.0 3-4 20 8 2.10 1.97 1.86 1.98 5.03-5 20 10 1.54 1.51 1.48 1.51 4.0 3-6 20 12 1.77 1.77 1.74 1.76 4.0 3-730 8 4.23 4.38 4.39 4.33 0.0 3-8 30 10 4.36 4.09 4.23 4.23 1.0 3-9 30 124.00 4.35 4.31 4.22 1.0

Example 4—Nanostructure Formed on Upliex Polyimide Substrate Film

A roll of polyimide film commercially available as 12.5 micrometer thickpolyimide films commercially available as “UPILEX-12.5S” from UbeIndustries, of Tokyo, Japan, was mounted within the chamber, the tapewrapped around the drum electrode, and secured to the take up roll onthe opposite side of the drum. The un-wind and take-up tensions weremaintained at 3 pounds (13.3 N). The chamber door was closed and thechamber pumped down to a base pressure of 5×10⁻⁴ Torr. The first gaseousspecies was hexamethyldisiloxane (HMDSO) vapor provided at threedifferent flow rates as outlined in Table 4 below, and the secondgaseous species was oxygen provided at a flow rate of 500 sccm. Thepressure during the exposure was around 10 mTorr and plasma was turnedon at a power of 6000 watts. The film was advanced at diverse linespeeds as outlined in Table 4 below. The Optical Transmittance (%Transmission), Haze (% Haze), and the Reflectance (% Reflectance) wasmeasured at each process condition. The values are presented in Table 4.A control in the form of completely untreated UPILEX film is alsopresented.

TABLE 4 HMDSO Oxygen Line Trans- Haze Sample Flowrate Flowrate Speedmission Delta Reflectance No. (sccm) (sccm) (ft/min) (%) (%) (%) ControlN/A N/A N/A 69.7 1.8  9.7  4-1 20 500 6 70.8 1.56 8.35 4-2 30 500 6 72.21.48 5.45 4-3 40 500 6 73.5 1.44 3.47 4-4 20 500 8 69.8 1.69 8.49 4-5 30500 8 70.9 1.64 6.73 4-6 40 500 8 71.6 1.51 5.18 4-7 20 500 19 69.1 1.659.14 4-8 30 500 10 70   1.61 7.79

Comparative Example 4C—Comparative Example (Nanostructure Formed onUpilex

Polyimide Film by the Methods of WO2011/139593)

A roll of Upilex polyimide film as described above was mounted withinthe chamber, the tape wrapped around the drum electrode, and secured tothe take up roll on the opposite side of the drum. The un-wind andtake-up tensions were maintained at 3 pounds (13.3 N). The chamber doorwas closed and the chamber pumped down to a base pressure of 5×10⁻⁴Torr.

The polyimide film was plasma treated in two passes generally asdisclosed in WO2011/139593. In the first pass, the first gaseous specieswas tetramethylsilane gas provided at a flow rate of 50 sccm and thesecond gaseous species was argon provided at a flow rate of 500 sccm.The pressure during the exposure was around 4 mTorr and plasma wasturned on and maintained at a power of 600 watts while the film wasadvanced at a speed of 37 ft/min (11.3 m/min). In the second pass, onlyone gaseous species, oxygen was provided at a flow rate of 400 sccm. Thepressure during the exposure was around 5 mTorr and plasma was turned onand maintained at a power of 5000 watts while the film was advanced at aspeed of 10 ft/min (3.05 m/min).

The micrograph of the surface obtained by the plasma treatment ofExample 4 is presented in FIG. 6, while a micrograph of the surfaceobtained in Comparative Example 4C is presented in FIG. 7. It can beseen that the single pass plasma treatment according to the presentinvention produces noticeably smaller features, and also provides adesirable variability in the height of the nanostructures.

Referring now to FIGS. 8a and 8b , graphs of atomic concentration vssputter time for embodiments of articles made according to Example 4 andComparative Example 4C below respectively, are presented. The figuresshow that the deposited layer comprising silicon using the method of thepresent invention is present in substantial amounts at greater depthswhen compared with the method previously disclosed in WO2011/139593 inwhich the silicon tapers off quickly as a function of depth. In the caseof the Comparative Example 4C, silicon concentration drops below 5%quickly, whereas for the case of Example 4, it is more than 5% for mostof the etched depth.

Example 5—Nanostructure Formed on Fluorinated Ethylene Propylene (FEP)Film

Sheet samples of fluorinated ethylene propylene (FEP) commerciallyavailable as “FEP-6322Z” from 3M-Dyneon of Saint Paul, Minn., extrudedto a thickness of 100 microns were attached to a PET carrier film whichwas mounted within the chamber, the PET film wrapped around the drumelectrode, and secured to the take up roll on the opposite side of thedrum. The un-wind and take-up tensions were maintained at 3 pounds (13.3N). The chamber door was closed and the chamber pumped down to a basepressure of 5×10⁻⁴ Torr. The first gaseous species was tetramethylsilanegas provided at a flow rate of 40 sccm and the second gaseous specieswas oxygen provided at a flow rate of 500 sccm. The pressure during theexposure was around 10 mTorr and plasma was turned on at a power of 6000watts while the tape was advanced at a speed of 6 ft/min (1.83 m/min).

The adhesion of the nanostructured surface was measured and comparedwith the bare FEP film without any plasma treatment and the results areas follows:

Average adhesion to nanostructured FEP Film: 63.53+−1.48 oz/in

Average adhesion to control unetched FEP film: 28.44+−0.77 oz/in

Example 6—Nanostructure Formed on Ethylenetetrafluoroethylene (ETFE)Film

A roll of extruded 100 micron thick ethylenetetrafluoroethylene (ETFE)commercially available as ET 6235 Z film by 3M Dyneon of St. Paul,Minn., was mounted within the chamber, the film wrapped around the drumelectrode, and secured to the take up roll on the opposite side of thedrum. The unwind and take-up tensions were maintained at 3 pounds (13.3N). The chamber door was closed and the chamber pumped down to a basepressure of 5×10⁻⁴ torr. The first gaseous species was tetramethylsilanegas provided at a flow rate of 40 sccm and the second gaseous specieswas oxygen provided at a flow rate of 500 sccm. The pressure during theexposure was around 7.5 mTorr and plasma was turned on at a power of6000 watts while the tape was advanced at a speed of 6 ft/min (1.9m/min).

Strips of the treated ETFE tape 4 inches (10.2 cm) long were handlaminated to several commercially available tapes, and these laminationswere pulled apart by hand to determine the quality of the adhesion. As acontrol, a similar test was performed on untreated ETFE tape. Theresults are shown in Table 1. (All the trial tapes are commerciallyavailable from 3M Company of St. Paul, Minn.)

TABLE 1 Adhesion to untreated Adhesion to Tape ETFE Film NanostructuredETFE Film 3M BLUE Painter's Poor, easy to 100%, adhesive split, transferTape remove from backing to ETFE film 3M SCOTCH 810 Poor, easy to 100%,adhesive split, transfer Office Tape remove from backing to ETFE film 3MGreen Silicone Medium, easy to Hard to remove, no adhesive Tape removetransfer 3M Packaging Poor, easy to 100%, adhesive split, transfer Taperemove from backing to ETFE film

The adhesion of the treated ETFE tapes was then assessed with regard toseveral double-sided adhesive constructions. A 2 inch (5.1 cm) longpiece of each double sided adhesive material was laminated at roomtemperature between two sheets of the nanostructured ETFE film. As acontrol, a similar test was performed on untreated ETFE tape. Thelaminates then were pulled apart by hand and the observations wererecorded in Table 2. (All the trial tapes are commercially availablefrom 3M Company of St. Paul, Minn.)

TABLE 2 Adhesion to Nanostructured Tape Adhesion to ETFE Film ETFE Film3M VHB Very poor, does not stick 100%, adhesive split 3M VHB AcrylicPoor, does hardly stick 100%, adhesive split Foam 3M Optically ClearPoor, does hardly stick 100%, adhesive split Adhesive

The adhesion of the treated ETFE tapes was then assessed with regard toseveral liquid adhesive adhesive constructions. The adhesives wereprepared according to the respective instructions. Then a drop of eachadhesive was placed between two pieces of ETFE film or NanostructuredETFE film. The adhesive then were allowed to fully cure for 24 hours. Asa control, a similar test was performed on untreated ETFE tape. Thelaminates then were pulled apart by hand and the observations wererecorded in Table 3.

TABLE 3 Adhesion to Adhesion to untreated Nanostructured Liquid adhesiveETFE control ETFE Film 3M Quick Set Epoxy Very poor, does not 100%, filmsplits, 5 min, clear adhere adhesive can not be removed 3M Scotch-Weld1838 Very poor, does not 100%, film splits, B/A Green Epoxy adhereadhesive can not Adhesive be removed Dow Corning RTV Very poor, does not100%, adhesive Sealant 734 (100% adhere splits, adhesive can SiliconeRubber) not be removed

While the specification has described in detail certain exemplaryembodiments, it will be appreciated that those skilled in the art, uponattaining an understanding of the foregoing, may readily conceive ofalterations to, variations of, and equivalents to these embodiments.Other modifications and variations to the present disclosure may bepracticed by those of ordinary skill in the art, without departing fromthe spirit and scope of the present disclosure, which is moreparticularly set forth in the appended claims. For example, theillustrated methods can be performed by hand or by different processingsteps than illustrated herein.

Furthermore, reference throughout this specification to “oneembodiment,” “certain embodiments,” “one or more embodiments” or “anembodiment,” whether or not including the term “exemplary” preceding theterm “embodiment,” means that a particular feature, structure, material,or characteristic described in connection with the embodiment isincluded in at least one embodiment of the certain exemplary embodimentsof the present disclosure. Thus, the appearances of the phrases such as“in one or more embodiments,” “in certain embodiments,” “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily referring to the same embodiment ofthe certain exemplary embodiments of the present disclosure.Additionally, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments. Thus, it is further understood that aspects of the variousembodiments may be interchanged in whole or part or combined with otheraspects of the various embodiments.

All references, patents, or patent applications cited in thisspecification are incorporated herein by reference in their entirety tothe same extent as if each individual publication or patent wasspecifically and individually indicated to be incorporated by referencein a consistent manner. In the event of inconsistencies orcontradictions between portions of the incorporated references and thisapplication, the information in the preceding description shall control.The preceding description, given in order to enable one of ordinaryskill in the art to practice the claimed disclosure, is not to beconstrued as limiting the scope of the disclosure, which is defined bythe claims and all equivalents thereto. Various exemplary embodimentshave been described. These and other embodiments are within the scope ofthe following claims.

The invention claimed is:
 1. A method of making a nanostructure,comprising: providing a substrate; mixing a first gaseous speciescapable of depositing a layer onto the substrate when formed into aplasma, with a second gaseous species capable of etching the substratewhen formed into a plasma, thereby forming a gaseous mixture; formingthe gaseous mixture into a plasma; and exposing a surface of thesubstrate to the plasma, wherein the surface is etched and a layer isdeposited on at least a portion of the etched surface simultaneously,thereby forming a nanostructure comprising nano-pillars or nano-columnshaving features of diverse height and aspect ratio.
 2. A method ofmaking a nanostructure according to claim 1, wherein the substratecomprises a (co)polymeric material, an inorganic material, an alloy, asolid solution, or a combination thereof.
 3. A method of making ananostructure according to claim 2, wherein the (co)polymeric materialcomprises a (co)polymer selected from poly(methyl methacrylate),poly(ethylene terephthalate), polycarbonate, cellulose, triacetate,polyamide, polyimide, a fluoropolymer, a polyolefin, a siloxane(co)polymer, a cyclic olefin (co)polymer, a polyurethane, andcombinations thereof.
 4. A method making a nanostructure according toclaim 3, wherein the (co)polymer is a polytetrafluoroethylenefluoropolymer and the surface of the substrate is substantiallycolorless after exposure to the plasma.
 5. A method of making ananostructure according to claim 1, wherein the substrate comprises atransparent (co)polymer.
 6. A method of making a nanostructure accordingto claim 1, wherein the first gaseous species comprises a compoundselected from the group consisting of organosilicon compounds, metalalkyl compounds, metal isopropoxide compounds, metal oxide compounds,metal acetylacetonate compounds, metal halide compounds, andcombinations thereof.
 7. A method of making a nanostructure according toclaim 6, wherein the organosilicon compounds comprise tetramethylsilane,trimethylsilane, hexamethyldisiloxane, tetraethylorthosilicate, apolyhedral oligomeric silsesquioxane, or a combination thereof.
 8. Amethod of making a nanostructure according to claim 1, wherein thesecond gaseous species comprises oxygen, a fluorocarbon, nitrogentrifluoride, sulfur hexafluoride, chlorine, hydrochloric acid, methane,or a combination thereof.
 9. A method of making a nanostructureaccording to claim 8, wherein the fluorocarbon is selected fromtetrafluoromethane, perfluoropropane, and combinations thereof.
 10. Amethod of making a nanostructure according to claim 1, wherein thegaseous mixture further comprises argon.
 11. A method of making ananostructure according to claim 1, wherein the nanostructure has adimension of less than about 400 nanometers.
 12. A method of making ananostructure according to claim 11, wherein the nanostructure has adimension of less than about 40 nanometers.
 13. An article comprising ananostructure further comprising nano-pillars or nano-columns havingfeatures of diverse height and aspect ratio made from the methodaccording to claim
 1. 14. An article according to claim 13, having aReflectance of less than 3% and a Haze Delta of less than 0.5%,optionally wherein the Reflectance is less than 2%.
 15. An articleaccording to claim 13, wherein the etched surface has at least onenanostructure with an aspect ratio greater than 2:1, optionally whereinthe etched surface has at least one nanostructure with an aspect ratiogreater than 15:1.
 16. An article according to claim 13, wherein thedeposited species is present over substantially the entire etchedsurface.
 17. The article according to claim 16, wherein theconcentration of the deposited species varies continuously according tothe depth from the exposed surface.
 18. The article according to claim13, wherein the exposed surface comprises silanol groups.
 19. Thearticle according to claim 13, further comprising a layer of pressuresensitive adhesive adhered to the exposed surface, optionally whereinthe pressure sensitive adhesive and the substrate are UV stable.
 20. Thearticle according to claim 13, wherein the exposed surface has a patternthat is random in at least one dimension, optionally wherein the exposedsurface has a pattern that is random in three orthogonal dimensions.